Vacuum pump



FIG. 1 is a bottom elevational view of the vacuum pump showing my design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a back elevational view thereof;

FIG. 4 is a top elevational view thereof;

FIG. 5 is a left side view thereof; and,

FIG. 6 is a right side view thereof. 

I claim the ornamental design for a vacuum pump, as shown and described. 